This study focuses on the chemistries of the biological antioxidants containing the Jahn-Teller metal ions Mn(III) and Cu(II), such as "superoxide dismatases" and those containing sulfur or selenium, a representative enzyme in the latter category being glutathione peroxidase. The work is concerned specifically with structure/reactivity relationships involving the above metal ions. A high resolution NMR probe for the study of selenium chemistry is being developed. We expect to be able to probe reactions involving selenium in living cells. The element Se is implicated in control of heart disease and certain cancers. Sulfur atom lability also is metal ion influenced. This lability can be studied kinetically by NMR. Sulfur atom lability and sulfide oxidation are important reactions occuring in the age of protein polymers and cellular oxidation. Zinc(II), in particular, influences the lability of sulfur atoms in organic disulfides. Its role mechanistically currently is unknown.